¿Qué códigos de función Modbus son compatibles?

Use 0x01, Read Coils, y 0x05, Write Single Coil. La pasarela expone coils, no holding registers.

¿Qué valores son válidos para Write Single Coil?

Los valores documentados son 0xFF00 para ON y 0x0000 para OFF. Otros valores devuelven la excepción 0x03, Illegal Data Value.

Configure la Unit ID como 0x01, es decir, el valor decimal 1.

The gateway supports the following Modbus function codes:

Code	Name	Description
0x01	Read Coils	Read coil status (status registers)
0x05	Write Single Coil	Write a single coil (command registers)

The gateway returns the following Modbus exception codes when an error occurs:

Code	Name	Description
0x01	Illegal Function	Function code not supported
0x02	Illegal Data Address	Coil address out of range
0x03	Illegal Data Value	Invalid value (neither 0xFF00 nor 0x0000)

All Modbus TCP communication uses the standard MBAP (Modbus Application Protocol) header:

Byte	Field	Value
0–1	Transaction ID	Set by client (echoed in response)
2–3	Protocol ID	0x0000 (Modbus)
4–5	Length	Number of following bytes
6	Unit ID	0x01
7	Function Code	0x01, 0x05
8+	Data	Function-specific payload